Bill and Robin's Not So Excellent Hypothesis

I think it’s strange to assume that a species which has had both language and complex social organization as long as we have would have a very simple-to-reduce reproductive drive.

We have vast amounts of cultural norms surrounding sex, relationships and reproduction, many of them are geared towards encouraging the former two. Generally these get treated as if they were merely methods of social control; ways to manage a population or secure political power through lineage. Isn’t at least somewhat plausible that the existence of these “cultural technologies” indicate that there are complex problems to be solved in human reproductive urges?

What I have always wondered: if fertility rates are declining because we are pursuing a rational utility maximizing lifestyle, then aren’t we modern westerners doomed by natural selection to lose out to a group that pursues overall resproductive success (success measured in a Darwinian sense) and not utility maximization?

One possible reason we may not be doomed is that our personal satisfaction may be entirely consistent with long term reproductive success. We may have fewer kids, for example, but perhaps they will receive better care and attention, thus conferring a survival advantage. That’s possible, but my intuition is that there is a substantial difference between the two goals, and that many will quite consciously limit their own and their progeny’s chances of long term reproductive success because they don’t want the responsibility of parenting.

It seems as if—if a subspecies of homo sapiens that was single mindedly focused on the reproductive success of themselves and their progeny—my lazy and hedonistic group would be doomed. We may have the happier lives, but evolutiuon doesn’t select for happiness.

Pandaemoni- the doom seems doubtful. For a start, Westerners vary in how many children they have. (For example, I know people who purposefully stopped with two children, others who purposefully had three, or four, or five). Plausibly, there may be some genetic component to the variation (what’s the identical twin data on number of children?)

So over generations, those people who have more children would gradually displace those who have fewer children, for whatever genetic reasons, within Western population, resulting in a higher average birth rate for the Western population.

Of courae it might be that another, non-Western group, with a higher birth rate, would outbreed the Westerners first. Or it may be that conditions would change so much that those factors that made for reproductive success in western countries in the 20th and 21st centuries would not make for reproductive success in the future, so it would all be up in the air again. So there are at least two options other than “doomed”.

Pandaemoni:

Your hypothetical family that has materially worse reproductive prospects with 10 children, but can afford 5, makes sense if we’re talking about the developing world. But in the modern western world, how much income do you really need to insure 10 kids are reproductively fit? That doesn’t require sending them to Harvard or buying them iPods.

I would guess that it’s at or about the poverty line, and that what we think of as investing in our children, say, by reading to them, taking them to soccer, or going to parent-teacher night, really isn’t doing much for their reproductive fitness. Once you feed them, don’t beat them, and have two parents physically present, you probably have most of the Darwinian bases covered.

I’m (sort of) with TracyW on this: If family size is heritable (whether genetically, or in the same sense that values are heritable), birth rates are going to go back up. There’s some sort of temporary shock going on.